1. Field of the Invention
The present invention relates to an in-vehicle radar system for transmitting an electric wave toward a target object and measuring the distance between the subject vehicle and the target object and the like, based on the electric wave that has been reflected by the target object and received by the in-vehicle radar system.
2. Description of the Related Art
To date, an in-vehicle radar system has been known in which, based on the time between a time instant when an electric wave has been transmitted (irradiated) forward from the subject vehicle and the time instant when the electric wave that has been reflected by a target object (e.g., a preceding vehicle) existing in front of the subject vehicle is detected, the distance between the subject vehicle and the target object and the like are calculated. It is required that such an in-vehicle radar system as described above has a function in which an electric wave is transmitted when the subject vehicle is in a moving state and, in contrast, when the subject vehicle is in a halt state, the transmission output power is reduced or the transmission is halted so that electric power is saved. As the in-vehicle radar system having a function in which, as described above, the transmission of an electric wave is halted when a vehicle is in a halt state, for example, an in-vehicle radar system, which is set forth in Patent Document 1, is known.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2006-21578
However, in a conventional in-vehicle radar system disclosed in Patent Document 1, the transmission of an electric wave is halted without any condition when the vehicle is in a halt state; therefore, it has been a problem that, even if the transmission is resumed at an appropriate timing, the state of a target object cannot be recognized and detected in a rapid and accurate manner.